“…9 Existing FOTs generally include: (1) trapping particles by the evanescent field of fiber tip near-field optics, including parabolic tips, 10 hollow fiber cone tips, 11 biconical cone tips, etc. 12 (2) Trapping objects using the tightly focused laser beam at the end of the fiber, including dual fiber OTs with flat-end faces, 13,14 dual fibers or multifiber OTs based on hemispherical self-lens end faces, 15 FOTs based on the end-face of Fresnel zone plates; 16 these methods improve the defect of insufficient NA of FOTs and enhance the application scenarios of FOTs. 17 At the same time, some special structures of FOTs have also emerged, such as four-core fiber with ring grooves, 18 graded index (GRIN) fiber tape with a microcavity, 19 OTs of printing metalens on fiber end face, etc.…”